Acute Hypoxia Tolerance of the Chick1

Acute Hypoxia Tolerance of the Chick1 R. R. BURTON AND J. C. CARLISLE Department of Animal Physiology, University of California, Davis, California 95616 (Received for publication January 16, 1969)

T

METHODS

Single Comb White Leghorn chicks, 0 to 31 days of age were exposed in groups of 10 to acute hypoxia in a nitrogen dilution chamber (described previously; Burton et al., 1969). The oxygen pressure in the chamber when 50% of the chicks were dead (LD6o) was determined, and the surviving chicks were removed. Their hematocrits and differential leucocyte counts determined 1 to 4 hours later by methods described elsewhere (Burton and Smith, 1967; Burton and Guion, 1968). Similar hematological measurements were made 1

This study was supported by National Aeronautics Space Administration Grant NGR-05-004008.

on chicks of the same age which had not been exposed to acute hypoxia. RESULTS

The hematology and hypoxia tolerance results are presented in Table 1. LDso's were difficult to determine in the 0 and 1 day chicks. Chicks which appeared to be dead were actually comatose and would revive within several minutes after removal from the chamber. An increase in the relative lymphocyte frequency (percentage of total leucocytes) with age was the only continuous change in the hematology noted. Similar findings in the lymphocytes have been reported previously by Burton and Harrison (1969). Hematocrits were similar to those reported previously for newly hatched chicks at sea level (Burton and Smith, 1969). The lack of hematological changes associated with acute hypoxia exposures in these young chicks indicates: (1) the chicks were not physiologically stressed or the chick is not capable of secreting enough corticosterone at this age to reduce the number of circulating lymphocytes, and (2) the chicks are not out of fluid balance— hemodilution or hemoconcentration. A relative and absolute lymphopenia in the chicken results from an environmental stressor and this lymphopenia has been correlated with an increase in the circulating corticosteroids (Burton and Guion, 1968; Burton et al., 1967; Evans, 1968). The newly hatched chick "0 day" is very tolerant to hypoxia, however, this tolerance diminishes rapidly until at 8 days of age it is only 5% greater than adult chickens with similar hematocrits.

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HE resistance of neonatal mammals to hypoxia is well known (Britton and Kline, 1945; Chiodi, 1963; Van Liere and Stickney, 1963; Fazekas et al., 1941). This tolerance decreases in all mammals until within a few days or weeks they are as susceptible as adults. The hypoxic tolerance of the newly hatched chick, however, has never been determined. Several investigations, however, have found that newly hatched chicks are not completely homeothermic until they are several days old (Romanoff, 1941; Randall, 1943; King, 1956; Lamoreux and Hutt, 1939; Deaton and Reece, 1968; Klieber and Winchester, 1933; Klieber, 1938). Since it is well known that poikiliothermic animals are very tolerant to hypoxia (Hock, 1964), it would be anticipated that newly hatched chicks would be very tolerant to reduction in environmental oxygen.

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R. R. B U R T O N AND J. C. CARLISLE TABLE 1.—The acute hypoxia tolerances {mm. Hg of oxygen pressure) and the hematology of groups of chicks of various ages

Age group (days)

Mean LDso body mass oxygen 1 (mm. Hg) (gms.) 11.9! 21.63 22.8 22.8 22.9 25.1 25.2 24.0 30.4 34.3 34.2 35.8 35.3 34.2 35.3 35.3 36.9 36.9 38.8 36.5

33.3 34.0 33.0 46.0 37.0 45.0 59.5 61.0 66.6 72.5 105.0 137.5 171.0

Hours

n

4

7 4 3 9 4 4 5 5 4 4 4 6 5 5 4 2 5 1 4 1

2 1 4 2 2 1 2 4 2 2 2 2 2 1 2

25.0±0.81 2 3 . 4 ± 1.50 24.5 + 2.60 23.3+1.56 22.6+3.13 22.1+1.08 23.2±1.10 24.2+1.01 24.1±0.74 26.1±0.80 25.8+1.71 26.0+0.68 28.6+0.35 28.5 + 0.72 28.9 + 0.57 31.3+0.25 27.9±1.08 24.0 23.0±2.61 27.0

Lymphocytes 2

n

(%)

7

17.1+3.40

9

26.7±4.30

4

32.5+7.40

4

34.0±2.12

3

47.4+4.06

5 5

47.0±3.90 32.4±4.90

n

Hematocrit

(%)

9

27.7±0.60

1

21.5

5 7

22.8+0.39 24.7±0.75

10

26.2±0.57

8 10

6

35.0+4.60

8 10 8

2 4 1

47.0±4.00 62.3+6.28 68

3 9

n

Lymphocytes

(%)

4

13.8+3.90

5

43.6±8.10

26.6+1.36 30.3+0.80

3

S 0 . 3 ± 11.30

30.5±0.87 29.3±0.63 24.0+2.00

4 4

57.8±7.60 65.5±3.40

26.0+2.89 24.4+0.75

7 6

72.3+3.36 69.7±7.15

1 2

50% mortality. Mean + standard error. s LDio.

T h e acute hypoxia tolerances of mature hens are directly correlated with their hematocrits (Burton et al., 1969): C.L. = 69.5e-° 0 2 1 i ?

(1)

Where: C.L. = conscious limit in mm. Hg oxygen pressure, H = hematocrit as a percentage. The conscious limit—the point where the bird is unconscious and exhibits a convulsive spasm—is just prior to death so t h a t the LD50 for each group should be quantitatively similar. Consequently, the C.L. for each group relative to its hematocrit was theoretically (mathematically) determined using equation (1). This value was compared to the LD 6 o for each age group of chicks as follows: C.L. - L D 6

H.T. ( %

<%)

.

C.L.

X 100

(2)

Where: H . T . = % increase in hypoxia tolerance; C.L. = calculated C.L. using equation (i);

LDso = mm. Hg of oxygen pressure where 1/2 of the exposed chicks died. T h e percentage increase in the hypoxia tolerance (H.T.), as determined by equation (2), was related exponentially to the age of the chicks (Figure 1): H.T. ( %) = 85.3e-°- 326A

(3)

Where: H . T . = same as equation (2); A = chick age in days between the ages of 0 to 8 days. r = (correlation coefficient) = 0.96; p<0.01. Chicks older than 8 days continued to have a 5 % increase in hypoxia tolerance, which is probably the differential in oxygen tensions between 5 0 % dead (LD50) and 100% survival b u t unconscious (C.L.). This exponential decrease in hypoxia tolerance with increasing age in the very young chick is qualitatively similar to the findings of Britton and Kline (1945) for rats. Using their data it was possible to develop the following equations:

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0 1 1.5 2 2.5 3 3 3.5 4 5 6 7 8 9 10 13 13 17 20 31

Control

Post hypoxia Hematocrit 2

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HYPOXIA TOLERANCE

85^ X

u o z < a: Ld o

80^ 75-

H.T

=85.3e

'0, 65-

-0.326A (0-8DAYS)

r = -0.96i

P<0.0l

60-

h-

< X

>X LU

4540-

3

35-

<

30-

z

25-

Ld

20-

(/) <

Ld CC O

15105— •

•

I

2

•

•

3 4

_j•

5

i• — i

6

••

i_ •

^-JL,

i•

i• — i

7

8

9 10 II 12 13 14 15 16 17 18 19 20

•

••

oo

•

I

•

•

•

•

•

W X

31

CHICK AGE (DAYS); A FIG. 1. The relationship of chick age with hypoxia tolerance. Hypoxia tolerance calculation is described in the text.

S.T. = 15.9e-°-131A

tinued to decline and they became much less tolerant to hypoxia than the adult. Where: This apparently does not apply to the chicken; since chicks older than 8 days S. T. = survival time in hours; continue to have the same hypoxia tolerA = age of the rat in days; r = (correlation coefficient) == 0.96; ance as the 8 day chick and adult chicken. p<0.01. DISCUSSION (4)

A qualitatively similar relationship was also found for the cat and rabbit (Britton and Kline, 1945). The rat and rabbit develop adult acute hypoxia tolerances at approximately 15 days of age, while the cat requires approximately 4 weeks, and the chick required only 8 days. Britton and Kline (1945) demonstrated that shortly after these young animals had developed hypoxia tolerances similar to those of their adults, their tolerance con-

Of interest to avian physiologists is the development of homeothermy in the newly hatched chick which occurs in the chick between the ages of 4 to 15 days (Randall, 1943; Romanoff, 1941; King, 1956; Lamoreaux and Hutt, 1939; Deaton and Reece, 1968). Temperature regulation in the chick is a complex physiological integration of several factors: increasing metabolic rate with age (Kleiber and Winchester, 1933; Kleiber, 1938), increasing

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o Q.

5550-

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R. R. BURTON AND J. C. CARLISLE

SUMMARY

The acute hypoxia tolerance of chicks 0 to 31 days of age was determined using a nitrogen dilution chamber. It was found that the newly hatched chick was approximately 85% more tolerant to hypoxia than adults. This tolerance was lost by 8 days of age at an exponential loss rate. These findings are qualitatively similar to those previously reported for immature rats, cats, and rabbits. The use of acute

hypoxia tolerance as a criterion of metabolic status in homeotherms is discussed. REFERENCES Britton, S. W., and R. F. Kline, 1945. Age, sex, carbohydrate, adrenal cortex and other factors in anoxia. Am. J. Physiol. 145: 190-202. Burton, R. R., and A. H. Smith, 1967. The effect of polycythemia and chronic hypoxia on heart mass in the chicken. J. Appl. Physiol. 22: 782-785. Burton, R. R., S. J. Sluka, E. L. Besch and A. H. Smith, 1967. Hematological criteria of chronic acceleration stress and adaptation. Aerosp. Med. 38: 1240-1243. Burton, R. R., and C. W. Guion, 1968. The differential leucocyte blood count: Its precision and individuality in the chicken. Poultry Sci. 47: 19451949. Burton, R. R. and J. S. Harrison, 1969. The relative differential leucocyte count of the newly hatched chick. Poultry Sci. 48: 451-453. Burton, R. R., and A. H. Smith, 1969. Induction of cardiac hypertrophy and polycythemia in the developing chick at high altitude. Fed. Proc. (in press). Burton, R. R., A. H. Smith, J. C. Carlisle and S. J. Sluka, 1969. The role of the hematocrit, heart mass and high altitude exposure in acute hypoxia tolerance. J. Appl. Physiol. 27: 49-52. Chiodi, H., 1963. Action of high-altitude chronic hypoxia on organisms during various growth stages. In: Perspectives in Biology, New York: Elsevier Publ. Co., pp. 336-347. Deaton, J. W., and F. N. Feece, 1968. Telemetering the body temperature of the broiler chick and effect of induced hypothermia. Poultry Sci. 47: 714-717. Evans, J. W., 1968. Avian metabolic adaptation to chronic acceleration. Doctorate Dissertation; University of California at Davis Library. Fazekas, J. F., A. D. Alexander and H. E. Himwich, 1941. Tolerance of the newborn to anoxia. Am. J. Physiol. 134: 281-287. Hock, R. H., 1964. Animals in high altitudes: reptiles and amphibians. In: Adaptation to the Environment. Am. Physiol. Soc, Wash., D. C , Chapter 53, pp. 841-842. King, J. O. L., 1956. The body temperature of chicks during the first fourteen days of life. Brit. Vet. J. 112:155-159. Kleiber, M., and C. Winchester. 1933. Temperature regulation in baby chicks. Proc. Soc. Exp. Biol. Med. 31:158-159.

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body temperature, stabilization of central temperature controls, as well as the development of adult feather cover. Since all of these conditions exist only in chicks several weeks of age it would appear that body temperature measurements may not be a good criterion of the metabolism characteristic of homeotherms. It is well known that poikiliothermic animals are extremely tolerant to anoxic environmental conditions as compared to homeothermic animals. The poikiliothermic animal exposed to hypoxic conditions simply reduce their oxidative metabolic demands to suit the occasion (Hock, 1964). This is not possible with completely homeothermic animals which have a minimum ("basal") metabolic rate. Consequently, it would appear that the response of an animal to a hypoxic environment should indicate its metabolic status as a homeotherm. The findings reported herein regarding acute hypoxia tolerance suggests that the chick has a homeotherm metabolism at 8 days of age. Interestingly, this corresponds closely with findings of others regarding homeothermy in the young chick using thermoregulatory criteria: Romanoff (1941) 4 to 5 days of age; Randall (1943) 10 to 15 days of age; Lamoreux and Hutt (1939) 4 to 7 days of age; King (1956) 10 days of age.

HYPOXIA TOLERANCE Kleiber, M., 1938. Metabolism body size and age in baby chicks. Proc. Soc. Exp. Biol. Med. 38: 793796. Lamoreux, W. F., and F . B. Hutt, 1939. Variability of body temperature in the normal chick. Poultry Sci. 18: 70-75. Randall, W. C , 1943. Factors influencing the tem-

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perature regulation of birds. Am. J.,Physiol. 139: 56-63. Romanoff, A. L., 1941. Development of homeothermy in birds. Science, 94: 218-219. Van Liere, E. J., and J. C. Stickney, 1963. Hypoxia. Chicago, Illinois: Univ. of Chicago Press, pp. 284-285.

Further Studies on Depletion of D D T Residues from Laying Hens 1

Department of Animal Sciences, Purdue University, Lafayette, Indiana 47907 (Received for publication January 20, 1969)

1

T HAS been the practice to destroy commercial laying hens that have become contaminated with chlorinated hydrocarbons. Recently, however, interest has developed in finding a method for more rapid depletion of residues which would allow earlier marketing of the eggs from contaminated layers. Stadelman et al. (1965) studied the persistence of selected chlorinated hydrocarbons after a measured exposure and found that up to 26 weeks were required to completely remove residues from abdominal fat and egg yolk. Stemp et al. (1965) simmered chicken meat containing chlorinated hydrocarbon residues for two-to-three hours at 190 to 200°F. and found that 10 to 90 percent of the residues were removed, depending upon which pesticide the meat contained. They reported heptachlor to be the most

1 Journal Paper No. 3554, Purdue Agricultural Experiment Station, Lafayette, Indiana 47907. Supported in part by grant from the American Poultry and Hatchery Federation. Submitted in partial fulfillment of the Ph.D. Degree. 2 Present Address: Virginia Polytechnic Institute, Poultry Science Department, Blacksburg, Virginia. 3 Present Address: National Dairy Products Corporation, Glenview, Illinois.

tenacious (only 10% removed) of all the pesticides studied. Wesley et al. (1966) studied the effects of feeding three levels of protein on depletion of DDT. They reported depletion of DDT residues to less than 0.01 p.p.m. (the limit of the detection method) in 16 weeks, with the use of a ration consisting of soybean meal, supplemented with vitamins and minerals, compared to 23 weeks for complete depletion in the control groups fed a standard laying ration. Emmens and Parkes (1939) discussed the action of testosterone in fat mobilization. They reported the most effective method of administration to be by injection. The objectives of this investigation were to determine the effects of the following three treatments on the depletion of DDT residues in the abdominal fat and yolks of commercial laying hens, following a measured exposure to the pesticide at: (1) three different periods of starvation, (2) two levels of androgen and (3) three levels of protein. The effects of low-fat and fat-supplemented rations, each with and without the fat soluble vitamins, on the depletion of DDT residues were also observed.

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R. L. WESLEY, 2 A. R. STEMP, 3 R. B. HARRINGTON, B. J. LISKA, R. L. ADAMS AND W. J. STADELMAN